EXPANDER OF CUTTING TYPE Russian patent published in 2001 - IPC

FIELD: drilling equipment, drilling tools. SUBSTANCE: proposed expander can be used to drill horizontal boreholes of large diameter to lay main service lines under natural obstacles and engineering structures. Expander comes in the form of body made of thick-wall pipe, disc with forks placed over circumference in which axles with rotary bits fitted with cutters are positioned and centering mount with ribs manufactured in the form of pipe and flange with guiding gusset plates. Width of forks in plane of axis of expander is less than diameter of rotary bits. Hydraulic monitoring checkers are installed in disc and flange of centering mount and flushing ducts are made in body. EFFECT: increased efficiency of expansion of shaft of borehole thanks to possibility of its working in reverse direction, liquidation of gutters and local distortions, raised wear resistance of expander. 2 dwg